Electrical apparatus



Dec. 24, 1935. J. w. ALLEN 2,025,144

ELECTRICAL APPARATUS Filed June 12, 193.

I N V EN TOR. Jbse ofi W A //6/;

Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE Eclipse Aviation Gorporation, East Orange,

N. 3., a corporation of New Jersey Application dune 12, 1933, Serial No. 675,475

1 Claim.

This invention relates to voltage regulators for dynamo electric machines, and particularly for generators driven from engines of variable speed, and operating to supply a variable or constant 5 current demand.

An object of the invention is to provide a regulator of the desired sensitiveness without the usual resort to vibratory make and break switches.

m A further object is to provide for the foregoing purpose, an automatically operated rheostat which varies the strength of the generator field immediately uopn the occurrence of a rise or fall in line voltage, and then holds the new setting steadily, and without the period of fluctuation which characterizes vibratory regulators.

In the preferred embodiment shown schematically in the accompanying drawing the rheostat is operated by an electric motor, the armature of which is connected across a resistance network in the form of a Wheatstone bridge, the connection being in such manner that the armature rotates only when the network potential balance is disturbed, and ceases to rotate as soon as the resulting change in line voltage restores equilibrium.

It is to be understood, however, that the maintenance of the electrical connections precisely as shown is not essential, the drawing being illustrative rather than definitive of the scope of the invention.

In the drawing, reference character G designates a generator armature rotatable through suitable mechanical connections (not shown) leading to an internal combustion engine crankshaft or other prime mover. The shunt field winding 6 of the generator is shown as connected in series with the coil 1 of a rheostat, the movable arm 8 of which. is electrically connected to one side 9 of the armature, through interposed leads l0 and I I, and mechanically connected to the armature E2 of an electric motor M through intermediate shafts Band I! carrying intermeshed worm and gear elements l5 and I6 respectively.

The field of the motor M is shown by way of preference as divided into two equal parts l6 and i1 electrically connected with resistance units l8 and IS in such a manner that they form opposite arms or links of a Wheatstone bridge, of

which the units I8 and 19 also constitute opposing arms of equal resistance, and the armature l2 takes the relative position occupied by a. galvanometer when the Wheatstone bridge is used for measuring purposes.

Preferably the units I8 and is are similar to the ballast resistors now commonly used in electrical circuits, and characterized by a tendency to maintain a substantially constant current under variations in voltage (at least within a predetermined range) and they serve effectively to main- 5 tain equally divided current flow through the windings i6 and ii in parallel, the current being drawn thereto by way of lead 29 and returned to the negative side 2d 01 the armature by way of leads 22 and 23. it)

Now, assuming the internal resistance of all four units it, ill, it and E9 to be equal at the normal voltage across leads 2i and 22, it follows that the potential drop from point a to point 1) will equal that from point a to point "0, l5 and therefore under this normal condition no current will flow through armature it, there being no potential difierence between points b and c. But in the event that the voltage rises or falls, the resulting change in the internal re- 20 sistance of units 08 and i9 relative to the internal resistance of units it and M will disturb the balance and cause current to flow through armature E2, the amount of current flow (and there-=- iore the degree of rotation of shafts i3 and i4, 25 and arm 8) being in direct proportion to the degree of unbalance. The resulting cutting in or out, as the case may be, of resistance l varies the strength of field l5 and to the same extent eliminates the voltage increment or decrement across 30 leads 2! and 22 as well as across the main lines 26 and 23 supplying a load 24 such as the anodicathode circuit of the electronic discharge tube or tubes of a radio set. When the voltage across these'two paths is thus restored to normal, equi- 35 librium is re-established in the bridge, and armature i2 is instantly de-energized by the resulting elimination of potential dlfierence across points 1) and 0". In order to insure immediate cessation of movement a spring-set brake 40 may be applied to the motor shaft, there being a solenoid or equivalent means (not shown) in circuit with the motor armature to release the spring pressure automatically whenever and so long as a potential difference exists across points b 45 and c.

Other features may be provided to supplement, or take the place of those above described, and certain of the features employed independently of the others, and for other purposes. Reference 50 is therefore to be had to the appended claim to determine the scope of the invention concretely exemplified in the foregoing specification.

What is claimed is:

In combination with a generator and rheostat 55 for controlling the output of the former, an electric motor energizable from said generator to vary the setting of said rheostat, and means for producing such energlzatlon whenever necessary to maintain the generator output substantially constant, said last named means comprising a Wheatstone bridge, a portion of which is constituted by the field windings of said motor, and the armature or said motor being connected across the central points of said bridge.

JOSEPH W. ALLEN. 

